Presently, in food processing conveyor applications, conveyors must be manufactured such that the conveyor belt can be removed and the entire conveyor frame assembly sanitized. Following sanitation, the conveyor belt must be reinstalled for continued operation. Numerous guidelines exist to regulate the type of conveyor assembly that can be used in a sanitary environment, such as in a food processing facility. Typically, these guidelines require that the conveyor frame assembly must be capable of being disassembled and sanitized. Since the conveyor frame assembly must be sanitized on a regular basis, the conveyor assembly must be capable of being quickly disassembled to allow complete cleaning. Preferably, the disassembly should require no tools.
The food processing guidelines for conveyors also require that the conveyors not include any areas that collect water after the conveyor has been washed down. If the conveyor includes areas that collect water, bacteria can form in the wet areas, which is unacceptable in a sanitary environment. Therefore, the conveyors used in the food processing industry must prevent water from pooling after the conveyor assembly has been washed down.
In many uses of sanitary conveyors, the conveyor belt is a plastic chain conveyor belt that is driven by a series of drive sprockets positioned near one end of the conveyor assembly. Each of the drive sprockets is positioned along a rotatable drive element such as a drive roller, which is coupled to a drive motor. Traditional conveyors include a drive motor and gear assembly that are located external to the drive roller. To conserve space, some conveyors include a drive motor and a gear reducer that are carried within the interior of the drive roller. Such internally driven drive rollers, known as motorized pulleys, have sealed components ideal for sanitary applications.
In conveyors that include internally driven drive rollers, the outer diameter of the driver roller is relatively large as compared to conveyors that include drive rollers driven by external motors. Since the internally driven drive roller has a relatively large outer diameter, the drive sprockets positioned along the outer circumference of the drive roller increase the overall size of the drive assembly. In most applications, it is desired for the conveyor to have as low a profile as possible to reduce the space requirements for the conveyor assembly.
Since the conveyor assembly is used in a sanitary environment, the drive sprockets must be movable along the length of the drive roller such that during cleaning, the areas of the drive roller under the drive sprockets can be cleaned. However, during normal conveyor operation, the drive sprockets are attached to the drive roller to prevent rotational and axial movement of the drive sprockets relative to the drive roller. The attachment between the drive sprockets and the drive roller facilitates torque transfer to the conveyor belt and avoids alignment problems between the drive sprockets and the conveyor belt.
Therefore, it is desirable to provide a keyed retention system that provides the driving engagement between the drive sprockets and the drive roller, and substantially maintains the axial position of the drive sprockets on the drive roller without the need for threaded fasteners. It is further desirable to provide a keyed retention system which is retained along the drive roller during normal conveyor operation yet can be easily released to allow the drive sprockets to slide freely along the drive roller during cleaning. It is further desirable to provide drive sprockets that have a low profile to provide for a drive assembly with an internally driven drive roller that has a low profile such that the overall height of the conveyor assembly can be as small as possible.